Explore the principles and applications of Wheatstone, Kelvin, and Maxwell bridges with this focused quiz. Enhance your understanding of how these classic circuits are used to accurately measure resistance and inductance in electrical engineering.
In a Wheatstone bridge circuit where R1 = 100 Ω, R2 = 200 Ω, and R3 = 150 Ω, what value of R4 will balance the bridge?
Explanation: The Wheatstone bridge is balanced when the ratio R1/R2 equals R3/R4; here, 100/200 = 150/R4 gives R4 = 300 Ω. The option 75 Ω would not create an equal ratio and is too low, while 100 Ω and 200 Ω do not satisfy the balance condition with the given values. Only 300 Ω ensures there is no voltage across the bridge’s galvanometer.
Which specific electrical property is the Kelvin double bridge designed to measure with high accuracy, particularly addressing errors due to lead and contact resistances?
Explanation: The Kelvin double bridge is specially designed to accurately measure very low resistances, where errors from lead and contact resistances can be significant. It is not intended for measuring high inductance or capacitance, which require different bridge types, nor is it involved in high voltage measurements. The focus on compensating for contact and lead resistances makes it uniquely suited for low resistance applications.
Which unknown component does a Maxwell bridge primarily help to determine in a circuit containing a standard capacitor?
Explanation: The Maxwell bridge is primarily used for the precise measurement of unknown inductance by balancing it against a known standard capacitor and resistors. While resistance is a secondary element in the bridge, its main function is not to find unknown resistance or measure capacitance directly. Conductance, which is the reciprocal of resistance, is not the focus of this bridge.
In a practical Wheatstone bridge setup, what is a common cause of measurement inaccuracy when using the bridge for low resistance values?
Explanation: When measuring low resistances, the resistance of the connecting wires (lead wire resistance) can introduce significant error into the results. High-frequency noise is generally not a primary concern in DC bridge circuits, and photodiode malfunction is unrelated to traditional Wheatstone bridge use. Temperature coefficient of capacitance is only relevant for capacitive components, not for simple resistance measurements.
In the Kelvin bridge, which ratio must be equal for the bridge to reach a balanced state?
Explanation: The balance condition for the Kelvin bridge requires that the ratio of the resistances in the arms adjacent to the galvanometer be equal to eliminate errors from contact and lead resistances. The ratio of total cell voltage to current is not a balance condition but defines Ohm’s law. Inductance and capacitance are not balanced in the Kelvin bridge, nor is the physical ratio of wire dimensions used.